Add the ability to undo token deletion

[mattrubin]

As suggested in a PR comment, the deletion confirmation alert could be replaced or augmented by the ability to undo deletion and restore a deleted token.

This feature would require underlying data model changes to store a "deleted" state for tokens. It's also worth considering whether the ability to restore a deleted token should be time-limited, and/or if there needs to be some way to permanently delete tokens, for security or privacy reasons.

[beaucollins]

If you think about it there's really not a lot of upside to deleting the secret from the keychain. I guess you could say it's more secure than having lingering secrets but in the end losing a secret seems worse.